Robotic systems are well known in manufacturing of many different objects, such as food products, automobile components, precision electronic assembly, etc. One traditional robotic system is commonly referred to as a “SCARA” (Selective Compliance Articulated Robot Arm), such as is shown in a simplified schematic representation in FIG. 1 and represented by the reference numeral 10. The SCARA system involves an arm moving from a first stop at a ready position to a second stop at a pick position (shown in FIG. 1) to acquire a work object 14, such as from a stack 16 of work objects. The arm 12 then moves to a third stop at a place position (not shown), such as on a manufacturing or packaging conveyor, to place the work object on the conveyor, and then the arm 12 moves back to the first stop or ready position, or to the second stop or pick position, depending upon a particular job. For the SCARA robotic system 10 to perform a standard pick-and-place operation, a gripper 18 secured to the arm 12 acquires the object 14 through standard grabbing apparatus, which may be mechanical, pneumatic, etc. As is apparent, the primary motion axes of the gripper 18 are all vertical and the arm 12 and its sub-members lie in a plane parallel to a floor (not shown) supporting the stack 16 and SCARA robot 10.
While such a SCARA robotic system 10 performs adequately with precision and frequently at very high cycle speeds, the requirement of many stops and starts is very energy inefficient. It is known that some SCARA robotic systems utilize so much energy that they experience up to a “13 G” force, or thirteen times the force of gravity for short durations to provide efficient cycle times. As the SCARA system 10 acquires, moves and places an object, the arm must execute repeated work and return motions. This pick-and-place cycle time is therefore only fifty percent efficient, and requires a lot of energy to move from a stop position through a work or return motion and back to another stop position.
In an effort to remove much of the inefficiency of the SCARA and other types of robotic systems, the present inventor and a co-inventor invented a “Multi-Head Robot System and Method Of Use” disclosed in U.S. Pat. No. 6,688,451 that issued on Feb. 10, 2004 to Derby et al, which Patent is hereby incorporated herein by reference. As shown in FIG. 2 in a simplified schematic of the Derby et al. multi-head robot system 20, an endless loop track 22 supports multiple robotic material handling devices 24 or heads. By having the robotic devices 24 secured to the track 22, the multi-head robotic system eliminates the return stroke of the SCARA robotic system 10. However, as the multiple heads 24 move over work objects so that each head 24 may pick an object, the heads must come to a stop at a pick position 26, and then move along the track to another stop at a place position 28. The multi-head system can achieve enhanced efficiency by having the multiple heads work in waves, such as a grouping of four or more heads (not shown), so that one stop acquires four work objects. Consequently, even though the return stroke of the SCARA system 10 is eliminated, the Derby et al. multi-head system nonetheless requires intermittent stops, which are energy inefficient. Additionally, the multi-head Derby et al. system requires care and precision in spacing of stopping points of the individual heads 24 and errors can produce collisions leading to substantial delays.
Accordingly, what is needed in the art is an improved robotic system that eliminates inefficient start-stop motions of large components of the system, and that also provides a variety of work axes of motion relative to movement of a work object from a first position to a second position.